The Chinese Journal of Process Engineering

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Study on sulfur removal from ferric phosphate by high-temperature calcination

Wenbo LOU Ying ZHANG Yang ZHANG Xiaojian WANG Jianzhong LI Shan QIAO Shili ZHENG Yi ZHANG

The Chinese Journal of Process Engineering 2022, 22 (2): 268-275. DOI: 10.12034/j.issn.1009-606X.221043

Abstract （1197）

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Iron phosphate is the main material for the synthesis of lithium iron phosphate battery cathode material, which is mainly produced by co-precipitation method of using ferrous sulfate and phosphate salt. The sulfur content in the iron phosphate prepared by the co-precipitation process in the sulfate system is high, which has to be removed by washing with large amount of water of around 60~100 tons per ton of iron phosphate, bringing a huge burden of sulfate-bearing wastewater treatment. To reduce the amount of wastewater from the source, this research proposed an alternative way for desulfurization by high-temperature calcination based on the feature of sulfate decomposition at high temperatures. The thermodynamic feasibility and kinetics of the desulfurization were studied. The results showed that the sulfur in ferric phosphate existed in the form of sulfate, which can be effectively removed by high-temperature calcination. A higher temperature was preferred for a more satisfactory desulfurization efficiency. Kinetic study uncovered that the desulfurization reaction order was 2, and the activation energy was 88.075 kJ/mol, indicating a chemical reaction control mode. The sulfur content in iron phosphate can be reduced to less than 0.01wt% by calcining at 1173 K for 10 min.

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Evaluation of safety performance and thermal stability of hard carbon anode for sodium?ion battery

Xinrong YANG Haiying CHE Ke YANG Chaoliang PAN Xiaozhen LIAO Zifeng MA

The Chinese Journal of Process Engineering 2022, 22 (4): 552-560. DOI: 10.12034/j.issn.1009-606X.220420

Abstract （809）

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As a promising energy storage system, the sodium-ion battery has attracted wide attention due to its rich sodium resources and cost advantages in energy storage and low-speed electronic vehicle application. With the development of the sodium-ion battery industry, battery safety is one of the key issues which is often caused by the heat loss of battery cells. In this work, the safety factors of sodium-ion batteries were studied, including thermal stability of hard carbon materials, over-discharge test, safety test (extrusion and acupuncture, etc.), and thermal runaway test. According to the first cycle discharge curve of a hard carbon coin cell, the solid electrolyte interphase (SEI) of hard carbon in different discharge potentials with differential scanning calorimetry (DSC) at 0.9, 0.5, 0.15 and 0.01 V, respectively were studied. The results showed that with the increase of sodium embedded in the hard carbon, the position of the exothermic peak appeared earlier and became more obvious and the presence of electrolytes reduces the stability of hard carbon embedded with sodium. The safety performance of full sodium-ion batteries can be evaluated by calorimetric analysis of the thermal runaway process of batteries. 1 Ah soft package batteries were prepared to study the over-discharge test and safety test. Compared with the non-over-discharge cells, cells over-discharge to 0 V had little difference in cycle performance after 500 cycles. The current density (0.1 or 1 C) had no significant influence on capacity recovery and cycle performance of the battery. The extrusion and acupuncture tests showed that the sodium-ion battery had good safety performance as the batteries were no fire and no explode. In addition, the thermal runaway test as calorimetric analysis was generally carried out by an accelerating rate calorimeter (ARC). The ARC test showed that the onset temperature of detectable self-heating were 136.6, 131.6, 136.3, 128.2, 166.6 and 138.6℃ at 80% state of charge (SOC), 60% SOC, 50% SOC, 40% SOC, 30% SOC and 0% SOC, respectively. Moreover, the thermal runaway occurred at 240.9℃ only at 80% SOC. It proved that the safety performance of the sodium-ion battery was good and the sodium-ion battery had the best safety performance at 30% SOC.

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Effects of hole distribution on flow field and noise for multi-hole plates

Qian LI Hua JI Donglin FENG Ziyang ZHANG Zongxing DUAN

The Chinese Journal of Process Engineering 2022, 22 (5): 601-611. DOI: 10.12034/j.issn.1009-606X.221131

Abstract （447）

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At present, the multi-hole plates with uniform hole distribution structure are widely used in the process industry to limit the flow and reduce the pressure, vibration and noise because of low manufacturing cost, simple structure, easy processing, easy installation and maintenance. In order to further improve the flow stability and reduce the flow noise, multi-hole plates of non-uniform hole distribution with different hole spacing, hole number, and hole diameter are designed with the equivalent opening diameter unchanged. Based on the numerical results, the velocity, pressure, reflux characteristics, jet convergence and flow development in the pipeline with different multi-hole plates are compared in detail to analyze the flow field characteristics. Moreover, the noise of multi-hole plates is numerically calculated by the acoustic analogy model. The observation points are set on the centerline and the section perpendicular to the flow direction to compare the spectrum characteristics and the overall sound pressure level. The numerical results show that the decrease of hole spacing with equal difference, the increase of hole number on the plate edge, and the increase of hole diameter without reducing the hole number can all effectively improve the flow stability and reduce the noise level of multi-hole plates without influencing the pressure drop ability compared with the general multi-hole plate with uniform hole distribution, and the maximum decrease of noise level is 5.62, 6.10 and 7.00 dB respectively.

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Ketopantoate production from glucose by combining biological and chemical steps

Yao YAO Xiyang LU Lin SHU Qinghui WANG Shaoqi SUN Jian HAO

The Chinese Journal of Process Engineering 2022, 22 (1): 97-107. DOI: 10.12034/j.issn.1009-606X.221036

Abstract （438）

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D-pantothenic acid (vitamin B5) is an essential vitamin to animals and has large markets in the feed, cosmetics, and pharmaceutical industries. The biochemical role of D-pantothenic acid in all organisms is to form the core of the structure of coenzyme A. Biosynthesis of coenzyme A from pantothenate occurs in all organisms, while the synthesis of D-pantothenic acid is absent from animals. Thus D-pantothenic acid is an essential nutrient to animals. Ketopantoate is an intermediate of pantothenate biosynthesis pathway. Ketopantoate can be stereoselectivity converted to D-pantoic acid and further used for D-pantothenic acid production. However, the economic production of ketopantoate is a bottleneck of D-pantothenic acid production from ketopantoate. Hence, this study provided a novel method for synthesis of ketopantoate by aldol reaction of α-ketoisovalerate and formaldehyde, and α-ketoisovalerate was produced from fermentation with glucose as the raw material. 25.2 g/L α-ketoisovalerate was produced by an engineering Klebsiella pneumoniae strain with glucose as the main carbon source. 19.9 g/L Ketopantoate was synthesized from formaldehyde and α-ketoisovalerate by an aldol reaction at basic conditions. The reaction parameters of reaction were optimized and a conversion ratio of 83.5% was obtained at reaction conditions of pH 13 and 45℃. The ketopantoate in the solution was converted to ketopantoyl lactone at acidic conditions of pH<3. Ketopantoyl lactone was extracted to isobutanol with an extraction rate of 50.9%. The organic phase was decolourized, and ketopantoyl lactone crystal was obtained after concentration. Ketopantoyl lactone was converted back to ketopantoate in an aqueous solution in the pH range of 7~10, and ketopantoate crystal was obtained after concentration. Ketopantoate production from glucose via α-ketoisovalerate as an intermediate was set up, which suggested a novel and competitive technical route to produce ketopantoate. The whole processes were combinated biological fermentation and chemical reactions and had a high conversion ratio. This method adopted renewable and cheap original materials rather than highly toxic raw materials. The optimal temperature of the reaction was 45℃, which was in mild conditions. Overall, a novel and promising method for ketopantoate and ketopantoyl lactone production was provided.

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Study on oxyfuel combustion behavior and the intrinsic kinetics of typically sized coal particles

Haolong BAI Liangliang FU Guangwen XU Dingrong BAI

The Chinese Journal of Process Engineering 2022, 22 (8): 1115-1123. DOI: 10.12034/j.issn.1009-606X.221256

Abstract （394）

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Oxyfuel combustion is a promising technology to facilitate carbon capture from combustion-generated flue gases. Circulating fluidized beds (CFBs), the major commercial-scale boilers, will play a significant role in the energy industry's transition from today's carbon-intensive to carbon neutral in the future. The types of boilers combust coals of wide screening particle sizes of 0~10 mm. The difference in coal particle size inevitably leads to a considerable variation in combustion characteristics, which has not yet been fully understood. In particular, little is known about the dynamic evolution behavior of combustion gas products and the intrinsic kinetics of the in-situ produced nascent char particles when these typically sized coal particles are combusted in fluidized beds. For this reason, an advanced micro fluidized bed reaction analyzer (MFBRA), integrated with a fast-responding process mass spectrometry, was employed to investigate the oxyfuel combustion behavior of two typically sized coal particles (i.e., 1.7~3.35 mm and 0.12~0.23 mm), typical of those in dense region and dilute region in CFBs, at 790~900℃. The use of MFBRA enabled the successful detection and characterization of the dynamic combustion process-sequentially occurring devolatilization and combustions of the in-situ produced volatiles and the nascent char particles. The results demonstrated that the combustions of volatiles and nascent char particles can have similar or different rates depending on the coal particle size. The two major successively occurring dynamic processes were distinctively identified and characterized for the coarse particles but not for the fine particles, which were featured with similar reaction rates for the two processes. The combustion of coarse char particles was rate-controlled by kinetics at low temperatures and changed to interparticle diffusion control at high temperatures. The combustion kinetics of the volatiles and nascent char were analyzed, and the corresponding values of activation energy were 107.2 and 143.9 kJ/mol, respectively.

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A novel process for preparation Ti-rich material from modified electric furnace titanium slag by phase deconstruction method

Yusheng ZHOU Guanzhou QIU Jianfa JING Fuqiang ZHENG Shuai WANG Feng CHEN Yufeng GUO

The Chinese Journal of Process Engineering 2022, 22 (5): 651-659. DOI: 10.12034/j.issn.1009-606X.221137

Abstract （376）

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In this study, a novel process for preparation rich-titanium material from modified titanium slag after melting in electric furnace by ammonium hydrogen fluoride leaching and hydrochloric acid leaching was proposed. The thermodynamic analysis of ammonium hydrogen fluoride leaching and hydrochloric acid leaching were investigated. The thermodynamic results of ammonium hydrogen fluoride leaching indicated that a small part of anosovite and the silicate can be decomposed, the silicate react with ammonium hydrogen fluoride leaching to produce sediment (CaMg2Al2F12), CaF2 and AlF3. The element of Si was converted to (NH4)2SiF6 existed in solution. The effects of ammonium hydrogen fluoride leaching conditions on the impurities extraction rate were investigated. The results indicated that the extraction rate of Si, Al, Ti, Fe, Ca and Mg were 93.55wt%, 28.03wt%, 3.88wt%, 20.50wt%, 3.40wt% and 2.45wt% respectively when the concentration of ammonium hydrogen fluoride was 15wt%, the liquid-solid ratio was 10:1, the temperature was 20℃ and the time was 2 h. The XRD results showed that the main phases in residue were rutile, anosovite and sediment (CaMg2Al2F12), the diopside was decomposed by ammonium hydrogen fluoride leaching. The thermodynamic results of hydrochloric acid leaching indicated that the sediment (CaMg2Al2F12), CaF2, AlF3 and the residual anovosite was decomposed by hydrochloric acid leaching. The effects of hydrochloric acid leaching conditions on the impurities extraction rate were investigated. The results of hydrochloric acid leaching indicated that the extraction rate of Ca, Al, Mg, Ti, Si and Fe were 86.78wt%, 62.33wt%, 92.31wt%, 18.08wt%, 40.23wt% and 75.36wt% respectively when the concentration of hydrochloric acid was 20wt%, the liquid-solid ratio was 8:1, the temperature was 120℃ and the time was 2 h. The main phase after hydrochloric acid leaching was rutile. The XRD results indicated that the sediment (CaMg2Al2F12) phase was solute by hydrochloric acid leaching. The titanium dioxide grade in rich-titanium material was 95.20wt%, the content of CaO was 0.49wt%, and the content of MgO was 0.48wt% which meet the need of boiling chlorination charge.

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Rigorous modelling and energy performance evaluation for PDH reaction gas separation and hydrogen purification

Xuantong LU Jin ZHAO Chun DENG

The Chinese Journal of Process Engineering 2023, 23 (1): 144-153. DOI: 10.12034/j.issn.1009-606X.221334

Abstract （372）

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Propane dehydrogenation is one of the main processes for propylene production and its reaction gas components are complex, containing products from main reactions and by-product components such as CO2 and CO from side reactions. To obtain polymer grade propylene and purified hydrogen product with a purity of more than 99.90 mol/mol, the separation process of the reaction gas of propane dehydrogenation and the recovery of hydrogen from hydrogen-rich tail gas is modeled and simulated in the Aspen software. The process includes main modules such as MEA decarburization, compressed cryogenic separation, deethanization, propylene distillation and pressure swing adsorption. The CO2 contained in the reaction gas would affect the purity of the propylene product, and it is difficult to remove in the cryogenic process. Thus the CO2 is first removed by the MEA solvent absorption. The reaction gas after decarburization and dehydration enters the deethanizer and the propylene distillation unit, and the hydrogen-rich tail gas enters the pressure swing adsorption unit for further purification. In order to reasonably utilize the energy of the propylene distillation tower, the heat pump distillation process is adopted for the energy integration. Compared with conventional distillation, the energy consumption of propylene heat pump distillation is lower. Sensitivity analysis and optimization of process parameters for hydrogen recovery by pressure swing adsorption are carried out to improve economy and energy efficiency. For the two-bed four-step pressure swing adsorption process, the effects of adsorption pressure, adsorption time and purge ratio on the purity and recovery of hydrogen products are analyzed, and the optimal operating conditions are determined. The simulation results show propylene and hydrogen products meet the requirements. The energy consumption per unit product is 267.46 kg standard oil/t propylene product and 474.44 kg standard oil/t hydrogen product. It has a certain reference significance for the simulation of the actual propane dehydrogenation reaction gas separation process and energy consumption estimation.

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Heat integrated double solvent extractive distillation process of tetrahydrofuran-methanol-methyl acetate-water

Chao LOU Ming LI Yi YUN Dehao WAN Deming YANG

The Chinese Journal of Process Engineering 2022, 22 (7): 882-890. DOI: 10.12034/j.issn.1009-606X.221316

Abstract （371）

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According to the characteristics of multiple binary azeotropes in the tetrahydrofuran-methanol-methyl acetate-water quaternary system, two distillation processes, conventional double solvent extractive distillation, and heat integrated double solvent extractive distillation were proposed. The solvent was selected based on the thermodynamic data calculated by the WILSON equation. The results showed that water was the most suitable solvent for tetrahydrofuran-methanol and methyl acetate-methanol azeotropes, and ethylene glycol was the most suitable solvent for tetrahydrofuran-water and methyl acetate-water azeotropes, the total solvent ratio was 0.65 and the ratio of ethylene glycol to water was 1.3. On this basis, taking energy consumption and total annual cost (TAC) as the evaluation indexes of the distillation process, the proposed conventional double solvent extractive distillation and heat integrated double solvent extractive distillation were simulated. The heat exchange network of the double solvent extractive distillation system was optimized by pinch analysis technology. The results showed that the cold utility consumption of the optimized heat exchange network was reduced by 44.12%, and the heat utility consumption was saved by 42.49%. Compared with the conventional double solvent extractive distillation process, the energy consumption of heat integrated double solvent extractive distillation process was reduced by about 43.29%, TAC was saved by approximately 26.89%, and the thermodynamic efficiency was increased by 3.25%. It can be seen that the heat-integrated double solvent extractive distillation process has better technical and economic advantages for separating the above quaternary system.

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Numerical investigation of gas-assisted sludge atomization and breakup based on VOF-DPM coupled model

Haihong FAN Zhou LI Binbin LI Lin LI Shuo SHANG Jiayang WANG

The Chinese Journal of Process Engineering 2022, 22 (12): 1633-1642. DOI: 10.12034/j.issn.1009-606X.221412

Abstract （370）

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Sewage sludge is an unavoidable by-product in the process of sewage treatment. Due to its characteristics of high pollution and difficult to treat, the efficient and harmless treatment of sludge is still facing certain challenges. A new sludge treatment technology, spray drying technology with relatively simple process and high value-added utilization after sludge atomization has a great promotion effect on sludge treatment. The gas-assisted atomizer has a good atomization effect on high-viscosity fluids, and can ensure a better atomization quality at a faster atomization rate. In the study of sludge atomization, many scholars have carried out certain researches, but there is no numerical simulation study of sludge atomization, and numerical simulation can be low-cost, more intuitive study of sludge atomization breakup, has certain advantages. In order to realize the numerical simulation of sludge atomization and breakup, computational fluid dynamics software is used to explore the influence of gas-assisted sludge atomization characteristics and operating parameters (gas velocity, gas-liquid ratio, spray angle) on the effect of sludge atomization. The results show that the density and viscosity of sludge gradually decrease with the increase of moisture content. Gas velocity, gas-liquid ratio and spray angle are the three most important operating parameters that affect sludge atomization and breakup. During the atomization process, the high-speed airflow makes the sludge vibrate and unstable at the front end of the atomizer, resulting in the tearing of the sludge and the breaking of the droplets. The density of droplets in the center area is greater than that in the edge area and there are a few large particles agglomerated. For sludge with moisture content of 87% and a density of 1.065×103 kg/m3, the atomization effect is the best when the gas velocity is 180 m/s, the gas-liquid ratio is 126.3, and the spray angle is 55°. The average particle size of the droplets is about 0.193 mm, and the experimental results are in good agreement with the simulated particle size, and the maximum relative error is 5.80%.

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Preparation of tannic acid-dopamine coating nanofiltration membrane for dye separation

Qin JIANG Ziyu LIU Sui ZHAO

The Chinese Journal of Process Engineering 2022, 22 (1): 89-96. DOI: 10.12034/j.issn.1009-606X.221041

Abstract （369）

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The tannic acid (TA)-polyvinylidene fluoride (PVDF) nanofiltration membrane is prepared by simply coating tannic acid and polydopamine. The chemical elements and morphology of the nanofiltration membrane surface are characterized by infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Meanwhile, the hydrophilicity and underwater anti-oil-adhesion performance of the modified membrane are also evaluated. Besides, the separation performance for dyes such as Direct red, Evans blue, Congo red, Reactive yellow, and Brilliant blue is explored. The result shows that the surface roughness of the obtained membrane increases slightly after modification. With the increase of TA concentration, the hydrophilicity of the membrane surface is significantly enhanced. When the TA concentration reaches 2wt%, the surface hydrophilicity of the prepared TA-PVDF nanofiltration membrane is almost stable, and the water contact angle of the modified membrane is 44.6°. Additionally, the obtained membrane with the underwater oil contact angle of 157.2° is characterized as a superoleophobic one. There is a strong interaction between the modified membrane and water molecules. On account of the hydration layer formed on the membrane surface, the obtained membrane can completely resist the contamination of oil under the water. The rejection rate of 2wt% TA-PVDF nanofiltration membrane is more than 96.5% for several dyes, and its permeating fluxes of Direct red, Evans blue, Congo red, Reactive yellow, and Brilliant blue all exceed 65.7 L/(m2?h?bar). In addition, the modified membrane keeps the permeance nearly unchanged during the dyes' separation process, exhibiting strong stability for dyes separation. Compared to the works published recently, the prepared nanofiltration membrane with 97% rejection rate for Congo red has a higher permeating flux. The obtained membrane shows a superior separation capacity and efficiency for the dyes, demonstrating a good application prospect in industrial dye wastewater separation.

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Dynamics performance of pressure swing distillation for acetone and cyclohexane separation

Chunhua ZHANG Lin ZHU Liping LÜ Qian ZHOU Shisheng JIN

The Chinese Journal of Process Engineering 2022, 22 (2): 249-257. DOI: 10.12034/j.issn.1009-606X.221022

Abstract （357）

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As significant chemical raw material and solvent, acetone and cyclohexane are widely applied in chemical industry. However, the mixture of them will form a minimum boiling homogeneous azeotrope at atmospheric pressure, which severely hinders the separation of them. Based on the advantages of pressure swing distillation (PSD) and the pressure sensitivity of the azeotropic mixture of acetone and cyclohexane, the investigation of the design and the simulation of PSD are implemented by Aspen Plus software. The results show that the purity of products achieve 99.9wt%. In order to save the total annual cost (TAC) and energy, based on the heat integration technology and economic optimization, it is implemented that the process enhancement with the minimum TAC as objective function. Furthermore, the TAC of the steady-state process of conventional, partial and full heat integration PSD are 3.64×105, 2.83×105, 2.76×105 $/y, respectively. Compared with the conventional PSD, the economic reduction rate of partial and full heat integration are 22.36% and 24.18%, respectively, and the full heat integration is most economical. In view of these, the different control structures are established by Aspen Plus Dynamics, and the anti-disturbance performance is investigated by changing the feed flow rate and composition, the dynamic performance of the full heat integration PSD process is assessed. The dynamic response results indicate that the control structure with a fixed reflux-to-feed flow rate ratio is better than the control structure with a fixed reflux ratio in terms of settlement time. However, the control structure with a fixed reflux-to-feed flow rate ratio cannot maintain product purity, up to the design value of 99.9wt%. For meet the goal of the requirements of products purities, an improved control structure with feed forward proportional (reboiler heat duty to feed flow rate ratio) control and composition-temperature cascade control are proposed, which can effectively ensure that the product purity reaches more than 99.9wt%.

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Improved sodium storage performance of layered oxide cathode materials via ZrO ₂ coating

Yang SUN Hong WANG Haiying CHE Xiaozhen LIAO Linsen LI Guijia CUI Weimin YANG Zifeng MA

The Chinese Journal of Process Engineering 2022, 22 (1): 72-78. DOI: 10.12034/j.issn.1009-606X.220379

Abstract （351）

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Lithium ion batteries have been successfully applied in portable electronic products, the application of lithium ion batteries is expanding to the fields such as large scale energy storage grid and electric vehicles. However, the considerably increased demand of lithium ion batteries might yield problems in the future with the limit of Li resources. Compared with lithium, sodium is abundant in the earth. Based on its resource and cost advantages, sodium ion batteries hold promise for low-cost energy storage and could be key for smart electric-grid of the future. To date, a large variety of cathode materials with satisfactory performance have been proposed. These cathode materials include layered transition metal oxides, Prussian blue analogues, polyanionic-type compounds and organic-based materials. Layered transition metal oxides NaxMO2 (M=Mn, Fe, Ni, Co, Ti, V, Cr) have been extensively investigated because of their higher capacities and industrial feasibility. Up to now, layered transition metal oxide NaNi1/3Fe1/3Mn1/3O2 has been established as a promising cathode materials for practical sodium ion batteries. Many works have also focused their efforts on NaNi1/3Fe1/3Mn1/3O2 over the years and studied its synthesis method, large scale synthesis, electrochemical reaction mechanism, coating, doping and thermal stability. In this work, ZrO2 coating NaNi1/3Fe1/3Mn1/3O2 cathode was prepared by a solid state method, and the coating effect was evaluated by electrochemical measurements as well as morphological, structural, and chemical composition analyses. The results showed that ZrO2 formed an inert protective layer on the surface of NaNi1/3Fe1/3Mn1/3O2, which effectively separated the contact between electrolyte and cathode material, alleviated the decomposition rate of electrolyte and inhibited the dissolution rate of metal ions, so as to significantly improve the cycle performance and high temperature performance of the battery. After ZrO2 coating modification, the cathode material was significantly improved compared with the uncoated cathode material at 55℃, and the capacity retention rate reached 83.6% after 100 cycles, which was higher than 75.2% of the uncoated cathode material. In addition, the stability of the coated NaNi1/3Fe1/3Mn1/3O2 cathode material was significantly improved after storage in air environment.

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Catalytic carbonylation of hexanediamine with diethyl carbonate to synthesis hexamethylene dicarbamate

Xitao YUAN Kelin HUANG Liguo WANG Peng HE Yan CAO Shuang XU Jiaqiang CHEN Huiquan LI

The Chinese Journal of Process Engineering 2022, 22 (3): 393-402. DOI: 10.12034/j.issn.1009-606X.220438

Abstract （348）

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Hexamethylene dicarbamate (HDI) is an important aliphatic isocyanate are often used in aerospace, aviation, and polymer materials. Compared with aromatic isocyanates, HDI does not contain a benzene ring and has a symmetrical carbon chain skeleton, which makes it light stable and highly decorated. Studies have shown that the non-phosgene method can be used to prepare HDI through the thermal decomposition of the key intermediate hexamethylene dicarbamate. In this work, 1,6-hexanediamine (HDA) and diethyl carbonate (DEC) are used to synthesis hexamethylene dicarbamate ethyl ester (HDEC) under the catalysis of manganese acetate anhydrous. The structure and purity of the self-made HDEC standard sample are determined by FT-IR, 1H-NMR and TG, and a quantitative analysis method is established. Furthermore, qualitative analysis of the main and side products of the reaction is carried out by GC-MS, and the reaction pathway is inferred. At the same time, the reaction parameters are optimized and the reaction mechanism is speculated. The results show that the reaction is achieved in two steps. First, HDA reacts with DEC to form a monosubstituted 1-(6-amino)-hexamethylene monocarbamate (HMEC) intermediate, the process is that manganese acetate attacks -NH2 at one end of HDA to form reactive intermediate I [H2N(CH2)6NHCOCH3], and reactive intermediate I reacts with DEC to form HMEC. Second, HMEC further reacts with DEC to form HDEC target product, the process is that manganese acetate attacks -NH2 at the end of HMEC to form reactive intermediate II [CH3CH2COONH(CH2)6NHCOCH3], and reactive intermediate (II) reacts with DEC to form HDEC. The CH3COOCH2CH3 reacts with Mn(OH)2 to form manganese acetate catalyst in the reaction process. In addition, DEC reacts with HDA and HMEC to form urea by-products during the reaction. Under the optimum reaction conditions, the molar ratio of DEC to HDA is 3.5:1, the reaction temperature is 120℃, the amount of anhydrous manganese acetate catalyst is 15% of HAD initial amount, the reaction time is 5 h and the rotating speed is 400 r/min, the conversion of HDA is 100% and the yield of HDEC is 89.6%.

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Research on the properties of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ high nickel ternary cathode material for lithium ion batteries

Cheng CAI Haiyan ZHANG Ying WANG Haikuo FU Ling HUANG Renheng TANG Fangming XIAO

The Chinese Journal of Process Engineering 2022, 22 (6): 754-763. DOI: 10.12034/j.issn.1009-606X.221194

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The Ni-rich cathode material (LiNi0.8Co0.1Mn0.1O2) has the advantage of high capacity and is the most potential cathode material for lithium-ion batteries. However, the poor cycle performance and rate capability limit its application. In this work, the structure evolution of the cathode material during the synthesis process and the influence of manufacturing temperature on the material properties were studied, and the potential causes of the structural changes and electrochemical degradation of the cathode material during the cycle were analyzed in detail. The physicochemical characterizations were conducted by employing the thermal gravimetric/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (HRTEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), etc. The cycle performance, rate performance, and other electrochemical properties were examined by electrochemical testing equipment. The results showed that the cathode material synthesized at 500℃ for 4 h and 750℃ for 14 h presents uniform particle size, good spherical structure, smooth surface of primary particles, compact arrangement, and stable crystal structure, which can alleviate polarization during cycling. Due to the proper particle size obtained at the optimized synthesis temperature, a relatively high initial discharge capacity, small volume changes, and slowly increased interfacial film resistance for the material were achieved, contributing to good Li+ diffusion kinetics. At 0.2 C, the first discharge-specific capacity was 186.2 mAh/g and the first charge-discharge efficiency was 82.5%. At 1 C, the discharge-specific capacity before and after 100 cycles were 185.1 and 175.2 mAh/g, respectively, and the capacity retention rate was up to 95.2%. The study of the synthesis and structural changes of Ni-rich cathode materials in this work can deepen the understanding of the materials and help improve the electrochemical performance of the materials.

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Multi-GPUs simulation of turbulent square duct flow in lattice Boltzmann method

Tao HU Xing XIANG Wei GE Limin WANG

The Chinese Journal of Process Engineering 2022, 22 (3): 318-328. DOI: 10.12034/j.issn.1009-606X.221118

Abstract （342）

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Compute unified device architecture (CUDA) and message-passing-interface (MPI) were used to implement the lattice Boltzmann method (LBM) multi-GPUs parallel algorithm on supercomputing system Mole-8.5E. The accuracy and effectiveness of the multi-GPUs parallel LBM algorithm was verified by the three-dimensional lid-driven cavity flow. Using this parallel algorithm, large-scale simulations of fully developed turbulent square duct flows with Reynolds numbers Reτ of 300, 600, and 1200 were carried out. Numerical results showed that when the grid size was less than the viscous sublayer, Δ+<5, the statistical error of the transfer characteristics near the wall was low, and the simulation accuracy met the need of engineering application. Meanwhile, when Reτ was 300 and 600, the simulation results at different grid sizes Δ+ showed that the LBM had a weak grid-dependent in the statistics of turbulence characteristics in the square duct central area, and when Reτ was 600, the averaged errors of the mean streamwise velocity predicted by LBM at Δ+=1.667, 3.750, and 6.250 compared with direct numerical simulation (DNS) were 1.357%, 2.994%, and 4.766%, respectively. The characteristics of turbulent square duct flow were studied when Reτ was 300, 600, and 1200, and the corresponding grid size Δ+ was 0.833, 1.667, and 3.333, respectively. The secondary flows were successfully captured, and the predicted mean streamwise velocity, pulsating root-mean-square (rms) velocity and other trends and results were consistent with the literature, which further verified the reliability of the single relaxation time (SRT) LBM, and the numerical results also provided a reference for understanding the turbulence characteristics of turbulent square duct flow at high Reτ. The simulation of turbulent square duct flow verified the potential of the SRT LBM multi-GPUs parallel algorithm in ultra-large-scale grid computing, and laid the foundation for further realization of the larger-scale numerical simulation required in practical engineering.

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Recycling of scrap lead paste to prepare lead powder by high efficiency electrolysis in choline chloride-ethylene glycol deep eutectic solvent

Haoming HUANG Juanjian RU Yixin HUA Xiao GENG Wenwen ZHANG Mingqiang CHENG Daoxiang WANG

The Chinese Journal of Process Engineering 2023, 23 (1): 107-114. DOI: 10.12034/j.issn.1009-606X.221422

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As a clean energy source without pollution during use, lead-acid batteries have received close attention. However, lead-acid batteries contain a large amount of polluting heavy metals, and random disposal will pollute the environment and affect the ecological balance. In industry, the recovery of scrap lead paste (SLP) is usually treated by pyrotechnics, but it consumes a lot of energy and also produces pollutants such as sulfur dioxide and lead dust. In view of the existing problems, finding new recycling processes has become a research hotspot. Deep eutectic solvents (DESs) are a new generation of green solvents and have received more and more attention in recent years. Because of their good thermal stability and wide electrochemical window, DESs are widely used in the fields of metal extraction and material preparation. In this work, the recycling of scrap lead paste to prepare lead powders by electrolysis is discussed in choline chloride-ethylene glycol deep eutectic solvent (ChCl-EG DES). Firstly, the phase composition of the scrap lead paste is analyzed by XRD, and the quantitative analysis of the scrap lead paste using Jade software shows that it mainly exists in the form of lead dioxide with a small amount of lead sulfate at the same time. And then, the electrochemical behavior of lead ion in 30 g/L SLP+ChCl-EG solution is investigated by cyclic voltammetry. The phase composition and microscopic morphology of the deposit product at different temperatures are examine using XRD and SEM techniques. The experimental results show that when scrap lead paste is added, Pb(IV) can be reduced preferential to Pb(II) due to the reducibility of ChCl-EG DES. Cyclic voltammetry indicates that the reduction of scrap lead paste to metal lead is a quasi-reversible process in ChCl-EG DES. The constant voltage deposition experiment show that when the temperature rises from 323 K to 363 K, the current efficiency rises from 67.26% to 96.06% and the specific energy consumption decreases from 961.57 kWh/t to 673.28 kWh/t. XRD and SEM results demonstrate that the deposit products obtained at different temperatures are pure metallic lead powders and their microscopic morphology are mainly rod-shaped and slight acicular.

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Preparation and performance of PB/ITO-PET flexible electrochromic films

Duoyin ZHU Zhihao JIN Wenli LI Qianyu WANG Rongcheng WU Yanbin CUI

The Chinese Journal of Process Engineering 2022, 22 (2): 176-185. DOI: 10.12034/j.issn.1009-606X.221005

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Due to the advantages of small volume, light weight and flexibility, flexible electrochromic (EC) devices have drawn much attention in various fields, such as flexible display screens, smart windows, information storage, electronic paper and energy-saving bracelets, etc. EC materials can be classified into two categories: inorganic and organic systems. Compared with organic EC materials, inorganic EC materials display good stability and reliability. Prussian blue and transition metal oxides are the two major classes of inorganic EC materials. Up to now, most reported EC devices in literatures are deposited on rigid substrates. It is still a major challenge to realize excellent EC devices on flexible substrates. Combining EC materials with flexible substrates is expected to have great application prospects in future smart clothes and implantable displays. In this work, potassium ferricyanide, potassium chloride and anhydrous ferric chloride were used as precursor. Prussian blue (PB) was deposited on ITO-PET flexible substrate by electrodeposition method to prepare PB/ITO-PET EC film. Scanning electron microscope, ultraviolet spectrometer and electrochemical workstation were used to characterize its microstructure and electrochemical performance. The experimental results showed that the light absorption rate of PB/ITO-PET EC film with the electrodeposition time of 200 s was 0.755 at the wavelength (λ) of 700 nm. The PB/ITO-PET EC film was colored and faded at low voltage (0.6 V/-0.3 V). The light modulation range, coloring/fading response time, coloring efficiency were 68%, 9 s/8 s and 108 cm2/C, respectively. The light modulation range and coloring efficiency of PB/ITO-PET EC film after 1000 coloring-fading cycles were 68% and 100.3 cm2/C. The coloring efficiency was 105.5 cm2/C after 500 bending, and the coloring efficiency and light modulation range of PB/ITO-PET electrochromic film were 91 cm2/C and 65% after 500 bending and 1000 coloring-fading cycles. Finally, a flexible EC device was assembled using ITO-PET as ion storage layer (counter electrode), gel electrolyte and PB/ITO-PET as working electrode, and its light modulation range and coloring/fading response time were 53% and 13 s/18 s, respectively.

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The influence mechanism of hydroxyl modification on the toluene adsorption by activated carbon based on molecular dynamics simulation

Bang XIAO Qing CAO Peiyong MA Hailin BI Pengcheng LI

The Chinese Journal of Process Engineering 2022, 22 (5): 660-670. DOI: 10.12034/j.issn.1009-606X.221125

Abstract （325）

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In this work, activated carbon models modified with different hydroxy contents were constructed by implanting hydroxyl groups at the edges of coronene. The physical properties, atomic partial charges and pore size distribution of the modified activated carbon model were studied by molecular dynamics and giant canonical Monte Carlo simulation, and the kinetic characteristics and adsorption mechanism of toluene in modified activated carbon were further analyzed. The results showed that the introduction of hydroxyl can improve the adsorption capacity of activated carbon to toluene, and hydroxyl content significantly affected the adsorption capacity. At high relative pressure, the best concentration of the hydroxyl group was 39.4%, and when hydroxyl concentration exceeded this value, the adsorption amount of toluene decreased. The strong electronegative oxygen atom in the hydroxyl group of modified activated carbon and the hydrogen atom in the methyl of toluene were combined to form a Lewis acid-base pair, which led to a stable adsorption structure and then increased the adsorption capacity of activated carbon to toluene. At low relative pressure, the main factors affecting the adsorption capacity were porosity and pore size. The modified activated carbon with hydroxyl content of 20.8% and 31.4% had massive micropores and a relatively compact structure, which was favorable for toluene adsorption. The self-diffusion coefficient of the toluene molecule in activated carbon was decreased by hydroxyl modification, and the diffusion coefficient was the lowest in activated carbon containing 39.4% hydroxyl. This was because the non-bond interaction between the toluene molecule and modified activated carbon hindered the movement of the toluene molecule. In addition, according to the variable-temperature adsorption research, the increase in temperature was not conducive to the adsorption of toluene by activated carbon since it was an exothermic process. This study can provide a theoretical basis for the improvement of the adsorption performance of activated carbon materials.

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Study on adsorptive separation property of CaY zeolite for ethylene glycol and 1,2-butanediol

Fan YI Peng HE Junya CAO Yan CAO Liguo WANG Jiaqiang CHEN Huiquan LI

The Chinese Journal of Process Engineering 2022, 22 (4): 448-457. DOI: 10.12034/j.issn.1009-606X.221007

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Ethylene glycol is an important petrochemical basic organic raw material, mainly used in the production of polyester, antifreeze, membrane, etc. China has abundant coal resources, which makes coal to ethylene glycol technology increasingly valued. As more and more coal to ethylene glycol plants is successfully running in China, the separation problem of ethylene glycol and 1,2-butanediol is urgently waiting to be solved. Selective adsorption is considered the most promising method because of its environmentally friendly characteristic and low cost. In this work, a fixed-bed column was used to separate ethylene glycol and 1,2-butanediol by using CaY zeolite as an absorbent, n-propanol was selected as the best eluent. In the fixed-bed column experiments, breakthrough curves were obtained and the dynamic adsorption characteristics were analyzed through breakthrough curves. The effect of operational conditions, such as flow rate and operating temperature were examined. The adsorption selectivity of ethylene glycol to 1,2-butanediol reached 1.90 at the temperature of 298 K and the flow rate of 0.8 mL/min. It can be found that the adsorption capacity of EG was much higher than 1,2-butanediol. The experiment results indicated that the breakthrough time and adsorption amount both decreased with increase of the flow rate and operating temperature. Modified Dose-Response models gave satisfactory fits to the experimental data of breakthrough curves in a fixed-bed column. At last, the adsorption sites of ethylene glycol and 1,2-butanediol were determined by Grand Canonical Monte Carlo (GCMC) simulation. It was found that the adsorption sites of ethylene and 1,2-butanediol almost overlapped, which meant ethylene glycol and 1,2-butanediol were competitive adsorptions in CaY zeolite. Moreover, the adsorption capacity of ethylene glycol was greater than 1,2-butanediol, which was consistent with the experiment result. The simulation result provided microscopic theoretical support for the experimental results. From these studies, CaY zeolite had the potential to be used as an effective absorbent for the adsorption and separation of ethylene and 1,2-butanediol.

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Catalytic cracking of n?hexane to light olefins by bimetallic modified ZSM-5-USY composite molecular sieves

Kailun ZHANG Nianming JIAO Ying ZHANG Pengbo HAO Guoxia ZHANG Hui WANG Zengxi LI

The Chinese Journal of Process Engineering 2022, 22 (4): 458-468. DOI: 10.12034/j.issn.1009-606X.221037

Abstract （322）

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Compared with steaming cracking, catalytic cracking is more appealing with much lower reaction temperature and adjustable distribution of the product (by changing the catalyst composition). In order to obtain efficient catalysts with high selectivity to light olefins for petroleum catalytic cracking, composite ZSM-5-USY zeolites were modified with single metal (e. g., cerium, yttrium, zirconium, manganese, and copper) or bimetals (e. g., zirconium-cerium, manganese-cerium, yttrium-cerium, and copper-cerium) by incipient impregnation. The physicochemical properties, including crystal structure, acidity, surface area, of the catalysts were characterized by XRD, NH3-TPD and BET. Catalytic activity of the prepared catalysts in cracking were evaluated by using n-hexane as a model compound for petroleum on a fix-bed reactor. The composition of the product was detected online by gas chromatography. The results showed that the composite molecular sieves modified by various metals exhibited quite different catalytic behaviors in n-hexane cracking, and the performance had close relationship with acidity content of the catalyts. Catalysts with higher weak acidity amount exhibited higher conversion of n-hexane and selectivity of C2~C4 olefins. The Ce-Zr co-modified molecular sieve showed excellent catalytic activity and high selectivity of C2~C4 olefins (57%) at 550℃. Steam treatment had significant influence on the acidity of Ce-Zr/ZSM-5-USY and distribution of the cracking products. After steam treatment, stability of the catalyst was significantly improved, and selectivity of C2~C4 olefins increased from 20.02% (when there was no steam treatment) to 57.55% (when the catalyst was steam treated for 4 h), but the n-hexane conversion rate decreased. Kinetics study of cracking of n-hexane over 0.25% Zr-0.5% Ce/ZSM-5-USY showed that this reaction was a first order reaction, and the activation energy was 88.93 kJ/mol.

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Preparation of 1,5?pentanediamine using bipolar membrane electrodialysis

Mengying DONG Yuzhu SUN Chen YANG

The Chinese Journal of Process Engineering 2022, 22 (4): 523-532. DOI: 10.12034/j.issn.1009-606X.221102

Abstract （313）

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1,5-Pentanediamine found in prokaryotic and eukaryotic organisms mostly is a natural polyamine with a variety of biological activities. In recent years, 1,5-pentanediamine has been becoming a focus since it can be used as the raw material for the preparation of nylon materials by biological methods and has been produced on an industrial scale. That means nylon materials can be produced at a lower cost by using the 1,5-pentanediamine (C5H14N2) as the raw material instead of 1,6-hexanediamine (C6H16N2) made by petroleum and chemical methods and it makes 1,5-pentanediamine have a wide range of application and business prospects. To extract 1,5-pentanediamine from post-fermentation broth, many methods have been tried. With the development of electrodialysis and ion-exchange membrane, bipolar membrane electrodialysis (BMED) has been widely applicated in an amount of areas since it can decompose salt into acid and base respectively by producing OH- and H+ without adding any other chemicals. In this study three-cell bipolar membrane electrodialysis was used in the main process of separation of bio-based 1,5-pentanediamine from post-fermentation broth. Simulated broths (1,5-pentanediaminium sulfate) were used to determine the optimum duration of EDBM process. The effects of current modes, current density, initial concentration of 1,5-pentanediaminium sulfate and the impurity positive ions in 1,5-pentanediaminium sulfate on BMED were evaluated principally with respect to alkali yield and partially with respect to efficiency and energy consumption. Membrane fouling, which mainly resulted from precipitation was also considered. The result also showed that the more satisfied recovery rate can be obtained at a higher current density. Furthermore, the impurity ions like K+ occurred in 1,5-pentanediaminium sulfate had no effect on base recovery rate, but it had an impact on the speed of recovery. Ultimately, the sulfate ions in the feed solution can be effectively removed and the recovery ratio of 1,5-pentanediamine reached 97.5% with low energy consumption 3.24 kWh/kg C5H14N2 at current density 20 mA/cm2. This process is environmental benignity and sustainable without any waste generated.

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Preparation and immunogenicity of alum-stabilized Pickering emulsion

Sha PENG Yufei XIA Xiaodong GAO

The Chinese Journal of Process Engineering 2022, 22 (2): 195-203. DOI: 10.12034/j.issn.1009-606X.221017

Abstract （309）

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Combating against the emerging pandemics, exploring the immunogenicity of the approved formulations is regarded as the optimal strategy for rapid clinical translation. To date, aluminum hydroxide adjuvant (termed as "alum"), which was composed by AlO(OH) has been used as the sole licensed adjuvant approved in China. Unfortunately, they seldom induce effective T cells-mediated immune response to produce efficient protection to meet the increasing demand for vaccine adjuvant. Therefore, the rational design of alum-based adjuvant may offer a novel and clinical-translatable vaccine platform for the potent immune activations and safety profile. In this work, alum particulate emulsion (APE) droplets were prepared by alum, and alum was adsorbed on the interphase between the US food and drug administration (FDA)-approved squalene and water. In contrast to the surfactant-stabilized emulsion, alum tends to adsorb on the squalene/water interphase, conferring a low surface tension and enhanced stability. After a series of optimizations, APE was prepared, with an average size of 2723.7±435.3 nm and a Zeta potential of +40.5±1.5 mV. Centrifugation demonstrated that 2.0 mg/mL was the minimum particle concentration to stabilize the emulsion droplets, which possessed just enough alum to avoid both the coalescence of the emulsions and the formation of larger aggregates due to excess in the continuous phase. SEM images indicated that alum was closely wrapped on the oil/water interphase, demonstrating a raspberry-like morphology. Additionally, CLSM images illustrated that the antigens were adsorbed on the squalene/water interphase of emulsion droplets in high efficiency. When treated with dendritic cells (DC), the enlarged internalization and lysosomal escape of the antigens were observed, indicating the potential for higher immune responses. After intramuscular injection, ELISpot results showed that IFN-γ secreted T cells increased by about 300% compared with that of alum accepted group, suggesting that prepared emulsion droplets were efficiently stimulated the cellular immune response. Collectively, with the feasibility of alum adsorptions on the oil/water interphase, as well as the bedside mixing of antigens, APE may provide insights for the development of a safe, accessible, and efficient adjuvant strategy for potent cellular immune response, which may offer an efficient strategy for clinically approved vaccine formulations.

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First-principles study of thermodynamic properties of lightweight dual-phase high-entropy alloy Al ₂₀ Li ₂₀ Mg ₁₀ Sc ₂₀ Ti ₃₀

Wei WANG Jin YANG Ning DING Xiaotao CHEN Biyu TANG

The Chinese Journal of Process Engineering 2022, 22 (3): 403-412. DOI: 10.12034/j.issn.1009-606X.221086

Abstract （309）

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High-entropy alloys (HEAs) have attracted plenty of attention over the past decade due to their excellent properties. Compared with face-centered cubic (FCC) or body-centered cubic (BCC) structure, hexagonal close-packed (HCP) structure is rarely found in the single-phase random solid solution of HEAs, and most existing HCP HEAs are composed of rare earth (RE) elements. As a novel HEA, Al20Li20Mg10Sc20Ti30 possess two phases including FCC and HCP phase. And the RE elements in Al20Li20Mg10Sc20Ti30 are only one (Sc), showing that it may open up a new way for the design of less-RE HCP HEAs. Moreover, the advantage of low density about 2.67 g/cm3 indicates the tremendous potential of it in aeronautics and prosthetic devices, etc. In this work, the structure stability and thermal properties of face-centered cubic (FCC) and hexagonal close-packed (HCP) Al20Li20Mg10Sc20Ti30 HEAs are studied from density functional theory in which the chemical disorder of completely random solid solution are treated using the special quasi-random structure (SQS). The theoretical lattice constants for both structures are in good agreement with experimental measurements, and HCP phase has better compressibility resistance due to slightly higher bulk modulus. Both HCP and FCC structures are thermodynamic metastable due to slightly positive formation enthalpies and the chemical bond in HCP is more covalent due to its broader pseudogap. Applying Debye-Grüneisen model, thermal properties of HCP and FCC Al20Li20Mg10Sc20Ti30 are studied under different temperatures. Results show that the bulk modulus of both phases decline gently as temperature increases, and bulk modulus of HCP phase is usually larger. By comparison, FCC phase possesses lager volumetric thermal expansion coefficient. Specifically, temperature dependence of thermal entropy for both phases, including vibrational and electronic contribution, is investigated in details, finding that the HCP has a larger entropy than FCC at investigated temperature range, and the entropies of both phases originate predominantly from the vibrational contribution.

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The influence of the structure of the interfacial compatibilizer on the interfacial state and performance of the PLA/PP blends

Bingyu FAN Xinliang CHEN Li YANG Shang GAO Yongjian XIE Zhenfeng WANG Ping WANG Jin LIU

The Chinese Journal of Process Engineering 2022, 22 (3): 413-420. DOI: 10.12034/j.issn.1009-606X.221087

Abstract （300）

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Maleic anhydride grafted ethylene-octene copolymer (POE-g-MAH) and glycidyl methacrylate grafted ethylene-octene copolymer (POE-g-GMA) were introduced into the polylactic acid (PLA)/polypropylene (PP) blends to prepare different structures and performance blended materials (PLA/PP/POE-g-MAH, PLA/PP/POE-g-GMA). The effects of compatibilizers with different structures on the regulation behavior of interface state and performance of PLA/PP blends were investigated by the torque rheometer, DSC, SEM, flat rheometer and electronic universal testing machine, etc. The results showed that both POE-g-MAH and POE-g-GMA could improve the interface morphology of PLA and PP, but compared with POE-g-GMA, the interface catalytic efficiency of POE-g-MAH was higher, which could induce PLA and PP more compatible, and catalyzed the formation of micro cross-linking structure at the interface between PLA and PP, which enhance the interfacial interaction between PLA and PP, and finally improved the mechanical properties of the material. When 4wt% POE-g-MAH was introduced, the tensile strength of the PLA/PP/POE-g-MAH blend reached 29.7 MPa, and the elongation at break increased to 39.3%, which was 8 times higher than that of PLA/PP sample. Also, the impact strength of the samples enhanced with the increase of the content of POE-g-MAH, and when its addition amount was 6wt%, the impact strength of the material reached 30.1 kJ/m2, which had a good balance of rigidity and toughness.

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Application of lignin epoxy resin synthesized in aqueous phase in wood adhesive

Yong WANG Yaqing YIN Qingyun LI Aixing TANG Lei ZHAO Youyan LIU

The Chinese Journal of Process Engineering 2022, 22 (5): 671-679. DOI: 10.12034/j.issn.1009-606X.221198

Abstract （298）

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In this study, a lignin epoxy resin suitable for wood adhesive was synthesized in an aqueous phase by using lignin as raw material. To study the effect of reaction conditions of lignin epoxidation on the hydroxyl and epoxy groups of lignin-epoxy resin and the bonding strength of plywood, the structure of lignin-epoxy resin was characterized by FT-IR and 31P NMR, and the thermal stability of lignin-epoxy resin was analyzed by TG and DTG. The results showed that the epoxidation reaction mainly took place in the phenolic hydroxyl group. And in the process of epoxidation, the additional amount of NaOH exerted a greater effect on the structure of lignin epoxy resin and the bonding strength of plywood than that of epichlorohydrin. With the increase in the amount of NaOH added in the reaction process, the number of epoxy groups in lignin epoxy resin increased gradually and the bonding strength of plywood showed a trend of increasing firstly and then decreasing. When the molar ratio of a hydroxyl group to NaOH of lignin was 1:1, the bonding strength of plywood made of lignin epoxy resin can reach the maximum, and the wet strength can reach 1.61 MPa, which exceeded the requirements of class II board in Chinese national standard (≥0.7 MPa). SEM was used to study the bonding mechanism, it was found that the structure of cured lignin epoxy resin was more stable and compact when the degree of epoxidation was increased, which led to the improvement of the bonding strength of plywood. However, an excessively high degree of epoxidation will increase the particle size of the adhesive particles, resulting in the inability of the adhesive to form a good mechanical interlocking structure with the wood, thereby reducing the bonding strength of the plywood. Furthermore, the synthesis process of lignin epoxy resin wood adhesive was simplified, the epoxidized system can be directly applied to the wood adhesive, and after 30 days of storage, the bond strength did not decrease significantly. Besides, compared with commercial UF resin wood adhesive, the bonding strength of UF resin can reach the level of commercial UF resin. The results showed that this method may have a great application prospect in the wood adhesive industry.

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Breeding of ε-poly-L-lysine high yield strain by ARTP and fermentation condition optimization

Zuwei XU Lihao JI Wenxiu TANG Liang GUO Xiulai CHEN Jia LIU Liming LIU

The Chinese Journal of Process Engineering 2022, 22 (3): 347-356. DOI: 10.12034/j.issn.1009-606X.221100

Abstract （296）

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ε-poly-L-lysine (ε-PL) is a natural homo-polymer of microbial origin, consisting of 25~35 L-lysine monomers, which is mainly produced by aerobic microbial fermentation and secreted to extracellular accumulation. Due to its wide antimicrobial spectrum and high safety, ε-PL has been successfully used as a food preservative. Besides, as a safe and green biopolymer, it has also been extensively applied in biomedical, chemical, and many other fields. Unfortunately, the efficient microbial production of ε-PL has reached a bottleneck owing to the limitations of low productivity, long fermentation period and unstable fermentation process, which can not satisfy the demand of industrialized production and brought obstacles to its popularity. To tackle these issues, S. albulus FMME-545RX with high tolerance to rifamycin was firstly screened and obtained by atmospheric and room temperature plasmas (ARTP) mutagenesis combined with ribosomal engineering, which could produce 2.44 g/L of ε-PL, with an increase of 105% in comparison with that of the parent strain S. albulus FMME-545. Then, a series of fermentation optimization strategies, including carbon sources regulation, pH control and dissolved oxygen (DO) regulation, were employed in increasing the production of ε-PL. The final results demonstrated that the mixed carbon source of glucose and sucrose fermentation was helpful to improve the metabolic intensity of bacteria; the addition of sodium citrate in the fermentation process can effectively improve the ability of the bacteria to resist the acidic environment; the optimum pH and DO values for product synthesis were 3.80 and 30%, respectively. Finally, under the controlled fed-batch fermentation, the production, productivity, and dry cell weight (DCW) of ε-PL reached up to 53.0 g/L, 6.63 g/(L?d), and 0.88 g/g, respectively, which were 130%, 131%, and 118% higher than those of the parent strain S. albulus FMME-545. Taken together, this study shows great potential for industrial production of ε-PL and the strategies described here also pave the way to the production of other value-added chemicals.

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Research on seat lip contact characteristics of cryogenic ball valve used in LNG receiving terminal

Zhenhao LIN Junye LI Zhijiang JIN Jinyuan QIAN

The Chinese Journal of Process Engineering 2022, 22 (6): 819-827. DOI: 10.12034/j.issn.1009-606X.221159

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The cryogenic ball valve is one of the indispensable fluid pipeline control devices in liquefied natural gas (LNG) receiving terminal. Its reliability directly affects the stability of the entire system, especially, when the ball valve has a serious valve seat seal leakage problem, which will seriously threaten the normal operation of industrial production and the safety of operators. In this work, based on the thermo-solid coupling method, the software of ANSYS Workbench was adopted to simulate the contact characteristics, including contact gap and contact pressure, of the lip seal of the cryogenic ball valve used in the LNG receiving station. Firstly, the distribution of temperature and Mises stress of lip seal under low-temperature conditions were analyzed. It was found that there were significant temperature differences in the lip seal, and the maximum temperature difference of the lip seal ring was 77℃. The temperature on the path from the inner lip seal ring to the outer lip seal ring decreased in order, which results in a significant increase of Mises stress. The maximum Mises stress reaches 204.92 MPa. Secondly, the contact characteristics of the lip seal under normal temperature and low-temperature conditions were analyzed. The results showed that the contact gap between the lip seal ring and the valve body and seat was unchanged, and the maximum contact pressure was evenly distributed along the circumferential direction under normal temperature conditions. While the contact gap of the lip seal increased and the contact pressure decreased under low-temperature conditions. The maximum contact gap reached -0.72 mm. Finally, the effects of different spring forced on the contact characteristics of the lip seal under low-temperature conditions were studied. It was found that the sealing performance of the lip seal could be improved to some extent by increasing the force. When the force of the spring was greater than 7000 N, the contact pressure between the lip seal ring and the valve body was greater than zero, and the precondition for sealing can be reached. This work has a certain reference value for the design and research of the seat seal of a cryogenic ball valve.

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CFD simulation of thermal runaway esterification reaction in stirred tank

Biqing CHEN Xiaoping GUAN Ning YANG Dingrong BAI

The Chinese Journal of Process Engineering 2022, 22 (8): 1053-1060. DOI: 10.12034/j.issn.1009-606X.221317

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Thermal runaway is one of the common risks in chemical process safety. Thermal runaway accidents of various scales cause a lot of economic losses every year. The runaway of batch stirred reactor is particularly dangerous due to the single way to control the reaction rate.From the view point of intrinsic safety, optimal design of reactor and operating conditions can fundamentally prevent thermal runaway. In batch-operated stirred tank reactors, impeller rotation can enhance flow circulation, turbulence intensity, mixing degree, and heat transfer, thus effectively preventing thermal runaway. In this work, according to the esterification reaction of propionic anhydride and isopropanol to produce isopropyl propionate and propionic acid under the catalysis of concentrated sulfuric acid, CFD simulation was carried out to simulate the thermal runaway esterification reaction in stirred tanks. The effects of impeller type (Rushton impeller, 30° pitched blade turbine impeller and 60° pitched blade turbine impeller), rotation direction, and baffle on the temperature evolution were studied. The simulated flow structures were used to explain the effects. Furthermore, divergence criterion was used to compare the performance of resisting thermal runaway for different impellers. The simulation showed that the radial flow agitator performed better than the axial flow agitator at the same rotation speed, and the performance order was Rushton impeller>30° PBTD impeller>60° PBTD impeller. For the 30° PBT impeller, when the operating mode changed from PBTD to PBTU, the capability to resist thermal runaway weakens, though the number of circulation zone increased. The situation of 60° PBT impeller was similar to that of 30° PBT impeller. The addition of baffle can substantially improve the thermal control in the reactor. This research provided fundamentals for design, optimization, and scale-up of reactors.

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Dispersion characteristics of droplets in the Q-type static mixer

Huibo MENG Jianbao WANG Yanfang YU Zongyong WANG Jianhua WU

The Chinese Journal of Process Engineering 2022, 22 (3): 338-346. DOI: 10.12034/j.issn.1009-606X.221104

Abstract （281）

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Static mixer is widely used in the process industry due to their advantages of compact structure, excellent intensification performance and continuous production. The enhancement mechanism of multiphase flow and dispersion mixing in Q-type static mixer (QSM) are not adequate, which restricts its application in green production of fine chemicals and green production of active pharmaceutical ingredient. The computational fluid dynamics (CFD) coupled with the population balance equation are used to simulate the flow and dispersion performance of droplets in the QSM. The discrete interval number of droplet size in the class method (CM) is set as 16 groups. The numerical simulation result in the classical helical static mixer has a good agreement with the experimental results. The dispersive mixing performance of different medium in RL-90-QSM are studied under Re=8000~24000. The effects of dynamic viscosity, interfacial tension, and phase volume fraction on the Sauter mean diameter (d32) are analyzed, respectively. The Q-type elements have good functions of splitting, recombination, and stretching. At higher Reynolds number and lower phase volume fraction, the average d32 values at different cross section obviously decrease in the first group of elements and then gradually decrease with the increase of mixing time. They become stable after z/l=10. The decreasing ratio of d32 at z/l=11.5 of benzene, toluene, cyclohexane and silicone oil 50 relative to the inlet droplet diameter (2.50 mm) are in the range of 78%~95%, 80%~96%, 73%~94% and 82%~96%, respectively. RL-90-QSM has the advantage of high efficiency and universality for dispersion mixing for the medium with different physical properties. The dispersion performance of droplets in liquid-liquid two phase flow with different continuous phase viscosities and discrete phase viscosities is similar. Compared with dynamic viscosity of discrete phase, the interfacial tension has much more influence on the final mixing result. As far as the restrained aggregation be concerned, the breakup performance of droplets is still predominant at dispersed phase volume fraction no more than 5%.

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Effect of CO ₂ content in annealing atmosphere and heating time on billet oxidation

Weidong ZENG Cuijiao DING Fangqin DAI Yue GUO Luwei PAN Ping′an CHEN

The Chinese Journal of Process Engineering 2022, 22 (3): 376-384. DOI: 10.12034/j.issn.1009-606X.220297

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Gas-fired heating continues to be the main heating method in the steel processing industry. In the reheating furnace before hot rolling, the annealing atmosphere can vary significantly because of the fluctuation of the calorific value of gas. When the calorific value of gas is low, the residence time of billet in the furnace will be prolonged, which will affect the production rhythm. For the above reasons, the oxidation of steel billet in reheating furnace is difficult to predict and control. To achieve quantitative understanding and prediction of steel oxidation in a reheating furnace, an experiment was conducted to study the oxidation behavior of steel billet in simulated atmospheres at the temperature of a soaking zone of the heating furnace. The results of steel oxidation in high purity nitrogen with selected CO2 content at 1523 K (1250℃) are obtained. The result shows that oxidation kinetics curves of samples in different CO2 content are divided into a linear phase and a parabolic phase. In the linear phase, the time and weight gains of the linear phase decrease with CO2 content increase. In the parabolic stage, the parabolic rate constant has a logarithmic relationship with CO2 content. The oxide film on the surface of the sample is divided into a loose compact layer and a loose layer. The compact layer is located on the outside of oxide film consisting of Fe3O4 and its reduction product FeO, while the loose layer is between compact layer and metal matrix and is mainly composed of FeO as well as a few proeutectoid Fe3O4 during cooling. There are voids and cracks inside of the loose layer, and the higher the CO2 content is, the more voids there are. Condensation of vacancy was believed to be responsible for the formation of voids, while increased CO2 content can promote the process. By observing the surface morphology, it can be inferred that FeO in the compact layer might be generated by the reduction of Fe3O4.

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Preparation and humidity-regulation performance of gelatin based natural polymer/graphene oxide composite microcapsules

Xueyan HOU Lihao NI Haitao ZHAO Wenbo ZHANG Yuqi ZHANG Jijiang WANG

The Chinese Journal of Process Engineering 2022, 22 (2): 214-221. DOI: 10.12034/j.issn.1009-606X.221035

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It is an environmental friendly and energy saving passive humidity regulation technology to use humidity control materials, which has been widely used in indoor humidity control, food packaging, cultural relic protection and other fields. The chitosan, liquid paraffin and graphene oxide were used as the microcapsule core materials. The surfactant-like hydrophilic and oleophilic chitosan-graphene oxide complex was formed by the electrostatic interaction between chitosan and graphene oxide. And the emulsion micelle was obtained emulsified by the combined assistance of emulsifier and chitosan-graphene oxide complex. Then using the emulsion micelle as template, the gelatin-based natural polymer/graphene oxide composite microcapsules (M-GO) were fabricated by the crosslinking of glutaraldehyde. The influence of graphene oxide dosage and emulsifying pH value on the micelle size and stability of emulsion was investigated. The microcapsules were obtained under the optimal emulsifying condition. The effect of graphene oxide on the structure and moisture adsorption/desorption performance of microcapsules were studied. The as-prepared microcapsules were characterized by Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption-desorption isotherms. The humidity-regulation performance was studied by measuring the moisture absorption and desorption rates. The results showed that emulsion micelle size was uniform with good stability when the dosage of graphene oxide was 3 mL (1 mg/mL) and the emulsifying pH value was 5.10. The results indicated that the microcapsules were successfully prepared by the interaction between graphene oxide, chitosan and gelatin. The microcapsule without graphene oxide showed a closed microsphere structure. After introducing graphene oxide, the microcapsule M-GO exhibited an open hollow shell and had larger surface area and pore volume, which was beneficial to adsorption moisture. The saturated moisture content and adsorption/desorption rate of M-GO in different humidity conditions were better than those of microcapsules without graphene oxide. It indicated that the introduction of graphene oxide can improve humidity-regulation performance by changing the microstructure and increasing the surface area for adsorbing moisture.

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Optimization and scale?up of fermentation process for succinic acid production by Escherichia coli FMME-N-26

Jia LIU Wenxiu TANG Xueming WANG Liang GUO Xiulai CHEN Cong GAO Liming LIU

The Chinese Journal of Process Engineering 2022, 22 (7): 853-862. DOI: 10.12034/j.issn.1009-606X.221265

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Succinic acid is considered to be one of the most promising bulk chemicals produced by white biotechnology and has a wide range of applications in industry. Microbial production of succinic acid has the advantages of environmental friendliness, and sustainable development, showing a good development prospect. However, a few issues remain with microbial production of succinic acid, such as the low yield, by-products accumulation and low productivity. In order to achieve the efficient production of succinic acid by Escherichia coli (E. coli) FMME-N-26, the fermentation conditions and feeding strategy were optimized in a 3.6 L fermenter. The process involved a two-stage fermentation, with aerobic cell growth followed by anaerobic conditions for succinic acid production. The optimal fermentation conditions were as follows: aerobic fermentation was transitted to anaerobic fermentation at 8 h, MgCO3 was used as pH neutralizer, 2 mmol/L betaine was added as osmoprotectants at 72 h, and glucose concentration was controlled to be 1~5 g/L in the anaerobic stage. The yield of succinic acid and the yield of glucose in anaerobic phase reached 119.2 g/L and 1.08 g/g (97% of the theoretical yield) at 72 h after optimized fermentation, which were 46.4% and 4.8% higher than those of the original fermentation, respectively. Only 2.37 g/L and 0.94 g/L of acetic acid, and lactic acid were accumulated as by-products, which were 37.1% and 49.2% lower than those of the before optimized fermentation, respectively. Then the scale-up production was realized in a 1000 L fermentation tank. The production of succinic acid yield, glucose yield and production intensity by E. coli FMME-N-26 were leading level at home and abroad. Taken together, this study provides a solid foundation for the industrial production of succinic acid and the strategies described here also pave the way to the production of other value-added chemicals.

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Research on recovery process and kinetics of gallium and indium from MOCVD production waste

Fu RAO Xiaohong ZHENG Xihua ZHANG Tianyi TAO Hongbin CAO Weiguang LÜ Zhi SUN

The Chinese Journal of Process Engineering 2022, 22 (5): 689-698. DOI: 10.12034/j.issn.1009-606X.221085

Abstract （273）

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In recent years, LED has been widely used in various lighting fields because of its energy-saving and environment-friendly characteristics. As a key part of LED products, epitaxial wafers are produced by metal-organic vapor deposition (MOCVD). With the rapid development of the LED industry, green and clean recycling of MOCVD production waste has attracted much attention. In this study, the leaching behavior and kinetics of Ga and In elements from MOCVD production waste were studied with sulfuric acid as a leaching agent. The effects of different types of leaching agents, H2SO4 concentration, solid-liquid ratio, leaching temperature and leaching time on the leaching efficiencies of Ga and In were systemically investigated. It was found that the leaching efficiencies of Ga and In can reach 67.50% and 91.46% under the optimal conditions of H2SO4 concentration of 3 mol/L, the solid-liquid ratio of 50 g/L, the temperature of 80℃, and the reaction of 120 min. The kinetics study showed that the leaching kinetics of Ga and In in the temperature range of 293.15~333.15 K was by the shrinkage core model, and the leaching process was controlled by surface chemical reaction and external diffusion mixing. At the same time, the results of XRD and SEM-EDS also confirmed the agreement with the shrinkage kernel model. The activation energies of Ga and In are 25.7 and 21.7 kJ/mol, respectively, when the leaching temperature was ranged from 293.15 K to 333.15 K. Based on the kinetics behavior of Ga and In leaching, the feasibility of enhanced roasting-acid leaching process was proposed and verified. It was found that the leaching efficiencies of Ga and In can be increased from 67.50% and 91.46% to 88.27% and 98.32%, respectively, under the enhanced roasting-acid leaching process. And gallium oxide byproducts were obtained. The findings from this research are expected to provide technical support and alternative for industrial recycling of critical metals from MOCVD production waste.

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Fluoride migration in the aluminum extraction process of roasting secondary aluminum dross with ammonium sulfate

Binghong LEI Honghui LIU Di ZHANG Yuming DONG Hongling ZHANG Taiping LOU Hongbin XU

The Chinese Journal of Process Engineering 2022, 22 (1): 108-117. DOI: 10.12034/j.issn.1009-606X.220402

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Recovery of aluminum from secondary aluminum dross by roasting with ammonium sulfate and leaching with water is one of the most important methods to harmlessly utilizing secondary aluminum dross. However, fluoride leaching toxicity of the leaching residue should satisfy the national standard's prescription (the mass concentration of inorganic fluoride is less than 100 mg/L). Thus, it is necessary to study the F migration in the Al extraction process of roasting secondary aluminum dross with ammonium sulfate and leaching with water. In this work, the regularities about migration and transformation of F in the process of extracting Al from secondary aluminum dross via roasting with ammonium sulfate and leaching with water was investigated by fluoride ion electrode, XRD, XPS, SEM and XRF. The results showed that prolonging the roasting time, elevating the roasting temperature and increasing the mass ratio of ammonium sulfate to secondary aluminum dross could accelerate the migration of F from secondary aluminum dross to roasting off-gas. Additionally, extending the leaching time, increasing the leaching temperature and increasing the liquid-to-solid ratio was beneficial to reduce the content and proportion of F in the leaching residue. About 43.85% of F released from secondary aluminum dross to roasting off-gas in the form of gas, 23.92% of F went into the leaching solution as fluorine ion, and 32.23% of F remained in the leaching residue in the forms of AlF3 and AlF3?3H2O under the most suitable conditions with the roasting temperature of 450℃, the roasting time of 2 h, the mass ratio of ammonium sulfate to secondary aluminum dross of 6:1, the leaching temperature of 85℃, the leaching time of 80 min, and the liquid-to-solid ratio of 6:1. Ammonium sulfate could be recovered from roasting off-gas by spraying after defluorination. Moreover, polyaluminum sulfate as a water treatment agent could be prepared from the leaching solution with the removal of F. The leaching toxicity of the leaching residue was accorded with the national standard.

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Green oxidation process for synthesis of 2-methyl-1,4-naphthoquinone from β-methylnaphthalene

Jinwen PAN Suohe YANG Guangxiang HE Xiaoyan GUO Haibo JIN Lei MA

The Chinese Journal of Process Engineering 2022, 22 (12): 1702-1709. DOI: 10.12034/j.issn.1009-606X.221426

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2-methyl-1,4-naphthoquinone (2-MNQ) is an important intermediate of K vitamins, which is widely used in medicine, pesticides, feed additives and other fields. However, this vitamin does not exist in nature, and artificial synthesis is the only way to produce 2-MNQ. In industry, vitamin K3 is prepared using 2-methylnaphthalene (2-MN) as raw material and chromic anhydride as an oxidant. This process produces a large amount of waste residue and wastewater containing chromium, causing irreversible pollution to the environment,and trace amounts of chromium in the product pose a threat to human health. Therefore, a new type of the green oxidation process was used for hydrogen peroxide oxidation. The process used 2-methylnaphthalene (2-MN) as raw material, (NH4)2S2O8 as initiator to prepare peroxygen with 30% H2O2 and glacial acetic acid under the catalysis of sulfuric acid. Acetic acid was added dropwise to the reaction solution to synthesize 2-methyl-1,4-naphthoquinone (2-MNQ) by oxidation, and its structure was characterized by ICIR, GC-MS, and LCMS, and the oxidation reaction mechanism and the type and content of by-products were verified. The main impurities were isomer 6-methyl-1,4-naphthoquinone and its by-products phthalic anhydride and 4-methylphthalic anhydride produced by excessive oxidation. The effects of catalyst, reaction temperature, reaction time, dosage of oxidizer and initiator on the yield and conversion of 2-MNQ were investigated. The conversion rate and yield of 2-MNQ were determined by HPLC (external standard method). The optimum reaction conditions were reaction temperature of 65℃, reaction time of 5 h, n(H2O2):n(2-MN)=26:1. The conversion rate of 2-methylnaphthalene was 99%, and the product yield was 34%. The innovation point of this work was to verify the reaction mechanism and the intermediate process in detail using the original external infrared, that was, the raw material 2-methylnaphthalene was oxidized by peracetic acid, the epoxidation reaction generated the intermediate, and then rearranged to generate 2-methylhydroxyquinone, and the oxidation continued to generate the target product 2-methyl-1,4-naphthalene quinone. The process has the characteristics of environment friendly, simple technology, mild operating conditions and easy availability of raw materials.The process uses 2-methylnaphthalene (2-MN) as raw material, (NH4)2S2O8 as initiator to prepare peroxygen with 30% H2O2 and glacial acetic acid under the catalysis of sulfuric acid. Acetic acid was added dropwise to the reaction solution to synthesize 2-methyl-1,4-naphthoquinone (2-MNQ) by oxidation, and its structure was characterized by ICIR, GC-MS, and LCMS, and the oxidation reaction mechanism and the type and content of by-products were verified. The main impurities were isomer 6-methyl-1,4-naphthoquinone and its by-products phthalic anhydride and 4-methylphthalic anhydride produced by excessive oxidation. The effects of catalyst, reaction temperature, reaction time, dosage of oxidizer and initiator on the yield and conversion of 2-MNQ were investigated. The conversion rate and yield of 2-MNQ were determined by HPLC (external standard method). The optimum reaction conditions were obtained reaction temperature 65℃, reaction time 5h, n(CH3COOOH):n(2-MN) = 26:1. The conversion rate of 2-methylnaphthalene was 98%, and the product yield was 35%. The innovation point of this paper is to verify the reaction mechanism and the intermediate process in detail using the original external infrared, that is, the raw material 2-methylnaphthalene is oxidized by oxyacetic acid, the epoxidation reaction generates the intermediate, and then the rearranges to generates 2-methylhydroxyquinone, and the oxidation continues to generate the target product 2-methyl-1, 4-naphthalene quinone. The process has the characteristics of environment friendly, simple technology, mild operating conditions and easy availability of raw materials.

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Adsorption and reaction of CH ₃Cl on both ZnO(001) and ZnO(100) surface based on the first principles calculation

Yazhuo ZHANG Jinhui ZHAN

The Chinese Journal of Process Engineering 2022, 22 (2): 240-248. DOI: 10.12034/j.issn.1009-606X.221064

Abstract （268）

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Based on the first principles method of density functional theory, the adsorption models of ZnO(100) and ZnO(001) surfaces were established to investigate the adsorption and reaction mechanisms of CH3Cl on ZnO surface through considering the adsorption sites, adsorption energy, charge density, density of states and transition state. The simulated results indicated that the adsorption of CH3Cl on both ZnO(100) and ZnO(001) surfaces was chemical adsorption. When CH3Cl was completely adsorbed, a weak chemical bond was formed between Cl and Zn atoms on ZnO surface. The adsorption of CH3Cl on ZnO(100) surface was more stable because the adsorption energy (-0.57 eV) of CH3Cl on ZnO(100) surface was lower than that (-0.42 eV) on ZnO(001) surface. When CH3Cl was adsorbed on ZnO(100) surface, the peaks of state density formed by the 3p orbital of Cl atom shifted to the left and the peak value near the Femi level was diminished comparing with that before the adsorption of CH3Cl. Thus the bonding effect of CH3Cl on ZnO(100) surfaces was more stronger and improved the stability of the system. During the dissociative adsorption of CH3Cl, the C atoms in methyl radical can be adsorbed to O(2a) and O(3a) on the surface of ZnO(100), respectively. The adsorption energy of CH3Cl dissociation adsorption on Zn(2a)/O(2a) site was -1.09 eV. There were three resonance peaks between O 2p and C 2p orbitals on the left side of the Fermi level. It was proved that there was a strong interaction between C and O atoms. On the other hand, the adsorption energy for CH3Cl dissociating on Zn(2a)/O(3a) site was -1.02 eV, and there was a resonance peak of O 2p and C 2p orbitals on the right side of Fermi level, indicating that there was a certain antibonding interaction between C and O atoms. The calculation results of reaction path way showed that the transition state energy of CH3Cl dissociation adsorption at Zn(2a)/O(2a) site was 1.69 eV, while it was 2.06 eV at Zn(2a)/O(3a) site. Therefore, the dissociation adsorption reaction of CH3Cl tends to occur at Zn(2a)/O(2a) site and to form the stable structure.

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Co-pyrolysis characteristics of caking coal with non-caking coal

Fujun LI Zhouen LIU Shiqiu GAO Xin JIN Yimin XIE Zhipeng HE

The Chinese Journal of Process Engineering 2022, 22 (5): 640-650. DOI: 10.12034/j.issn.1009-606X.221084

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The decaking technology with co-pyrolysis of caking coal and non-caking coal was brought out to destroy the caking property of caking coal. And the properties of decaking and co-pyrolysis of caking coal with the decaking technology were studied with co-pyrolysis experiments using TG-MS and fixed bed pyrolyzer. It could be seen from TG-MS experiments that the caking property of the mixed coal produced by caking coal and non-caking coal was smaller than that of caking coal. And pyrolysis of caking coal can be improved by the addition of non-caking coal. The co-pyrolysis characteristics of the mixed coal were the combined action of those of the two single coals. And it could be seen from the fixed-bed pyrolysis experiment that the decline of caking property of the mixed coal rised with smaller particle size of coal and the descent of the ratio of caking coal to non-caking coal in the mixed coal (XX:XF). And the agglomerate was slight. With the descent of XX:XF, the content of char reduced in pyrolysis products, but the contents of tar, coal gas and carbon deposition and water were higher. With the descent of XX:XF, the fractions of distillation cut <170℃ and 230~300℃ in tar from mixed coal first rise and then decrease and reach peak value at XX:XF=6:4~3:7, and the fractions of distillation cut of 170~210℃, 210~230℃, 300~360℃ rised, while the fraction of distillation cut >360℃ decreased. With the descent of XX:XF, the contents of H2, CO and CO2 in coal gas from mixed coal become larger, but the contents of CH4 and C2~C3 became smaller. While the contents of H2+CO+CH4 became first smaller and then larger with XX:XF and reached peak value at XX:XF=5:5~3:7. And with the descent of XX:XF, the char from mixed coal had smaller C/N and C/H, larger amplitudes of increase of C content and reduction of content of N and H, larger special surface area, more and larger internal pore structure, lower ignition temperature, more complete combustion.

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Numerical simulation and operating parameter optimization of three-stage piston pusher centrifuge

Liqun ZHOU Zhiming WANG Zhennan WANG Yuping LI Zhizhong HUANG

The Chinese Journal of Process Engineering 2022, 22 (3): 329-337. DOI: 10.12034/j.issn.1009-606X.221078

Abstract （259）

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In response to the need for improvement of the new three-stage piston pusher centrifuge such as the gradual increase in production capacity, the diversification of raw materials and the optimization of the centrifuge structure, the vital influence of operating parameters on the erosion phenomenon and separation efficiency in the drum during the separation process has been confirmed. The simulation software's pre-processing parameters were concluded based on the raw materials' experimental sampling and the corresponding piston pusher centrifuge provided by the manufacturer, starting from the material's particle size. The three-stage piston pusher centrifuge was modeled in three dimensions, using discrete phase and continuous phase. The solid-liquid separation process was simulated by the combined method and the dense discrete particle model (DDPM) was used to simulate the erosion process. Finally, the data was analyzed in combination with experiments to obtain the size and rules of the erosion of each structure by the particles during the separation process and the new equipment's optimal operating parameters. It was concluded that when the particle size dm of sodium chloride particles was between 0.070 mm and 0.200 mm, as the particle size increased, the solid phase's erosion inside the centrifuge drum became greater. Using prototype experiments and CFD numerical simulation combined with response surface analysis, the interactive influence of each factor of the response model was evident. The influencing factors from high to low were drum's rotating speed, feed concentration, and push frequency for the separation rate. For the erosion rate, the influencing factors from high to low were the drum's rotating speed and the feed concentration. Considering higher separation rate and lower erosion rate as evaluation indicators, the optimal value obtained as push frequency of 40 times/min, drum's rotating speed of 1431 r/min, and feed concentration of 60%. Compared with the experimental data, the simulation error was within the acceptable range.

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Microstructure changes of saline?alkali soil influenced by fly ash-based soil conditioner

Shaowen DONG Shuhua MA Mo CHU Xiaohui WANG Yuejiao WANG Chenxu LIU Fenglan HAN

The Chinese Journal of Process Engineering 2022, 22 (3): 357-365. DOI: 10.12034/j.issn.1009-606X.220371

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The field test results have shown that the physical and chemical properties of saline-alkali soil can be significantly improved by adding fly ash-based soil conditioner. However, at present, the improving mechanism of fly ash-based soil conditioner is not clear, and the structural change law of soil particles is not understood. So this work took the typical saline-alkali soil in the Yinbei area of Ningxia Hui Autonomous Region as the research object, studying the microstructure of saline-alkali soil particles under the action of fly ash-based soil conditioner by X-ray diffraction (XRD), infrared spectroscopy (FTIR), specific surface automatic physical adsorption instrument (BET) and scanning electron microscope (SEM). The results showed that the main components of soil minerals did not change, but a new crystal phase calcite was found in the soil after the fly ash-based soil conditioner was added and the pH value of the soil was greatly reduced from 9.01 to 7.66. The infrared absorption of the soil with fly ash-based soil conditioner changed little, but the absorption peaks of Si-O-Si and organic matters were slightly enhanced. The soil microstructure changed greatly with the increase of the conditioner addition since the small soil particles began to aggregate and the soil porosity gradually increased. Taking the 2.5wt% group as an example, its porosity was up to a level of 21.30% after 15 days and 25.29% after 30 days, which was about twice that of the blank control group. The specific surface area of soil particles increased slightly from the initial value of 23.06 m2/g to 25.55 m2/g after 30 days. The above results proved that fly ash-based soil conditioner could not only alleviate the problem of land salinization, but also realized the large-scale consumption of fly ash solid waste.

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Thermodynamic model for the phase equilibrium of cerium carbonates in the NaCl-H ₂O system

Feng LUAN Daoguang WANG Junfeng WANG Jianwei ZHANG Penglei CUI

The Chinese Journal of Process Engineering 2022, 22 (8): 1103-1114. DOI: 10.12034/j.issn.1009-606X.221348

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Cerium carbonates are important precursors for the production of CeO2, which have a decisive effect on the properties of CeO2. The crystal characteristics of cerium carbonate compounds depend on the control of supersaturating in reactive crystallization, and the solubility of cerium carbonate compounds in the NaCl-H2O system are important basic data. In this work, cerium carbonates were synthesized by homogeneous precipitation method at the temperature range of 298.15~363.15 K. The generated solids were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM) and thermogravimetric analyzer (TG). The results showed that Ce2(CO3)3?8H2O was obtained below 323.15 K and transferred to CeCO3OH above 343.15 K. The solubility of the two cerium carbonate compounds in the NaCl-H2O system were determined by the classical isothermal method. The results showed that the solubility of Ce2(CO3)3?8H2O increased with the increase of temperature and concentration of NaCl, while the solubility of CeCO3OH increased with the increase of concentration of NaCl, and decreased with the increase of temperature. The solubility of Ce2(CO3)3?8H2O in water at 298.15 K was 4.08×10-6 mol/kg, which was of the same order of magnitude as the solubility of cerium carbonate [Ce2(CO3)3] that was 2.17×10-7~2.17×10-6 mol/kg at 298.15 K. The results indicated the reliability of the experimental data measured in this work. A thermodynamic model for predicting the solubility of Ce2(CO3)3?8H2O and CeCO3OH in the NaCl-H2O system was finally established by using the ELEC-NRTL equation embedded in the Aspen Plus platform. The solubility products of Ce2(CO3)3?8H2O and CeCO3OH were obtained by regression of their solubility data in water on the basis of an infinite dilution assumption. The species such as CeCO3+, CeOH2+, CeHCO32+ were introduced into the thermodynamic model on basis of the speciation method and their equilibrium constants were calculated by Van't Hoff isothermal formula. The new ion pair parameters of Ce3+-HCO3- and Ce3+-Cl- were obtained by regression of the experimental data to improve the predictive ability of the new model. The predicted values of the established thermodynamic model were well in agreement with the experimental data.

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